Over the weekend, Apple released an update for a kernel extension blacklist used by System Integrity Protection on OS X El Capitan. This blacklist is a security measure to help Apple block kernel extensions which have been found to be harmful or problematic for OS X. This update belonged to a category of updates which Apple has set to install automatically and in the background, so its installation would have been both automatic and invisible.

Unfortunately, this blacklist update appears to have inadvertently contained the kernel extension information for Apple’s own Ethernet drivers. This is a problem because blocking the Ethernet drivers means your Mac will not be able to connect to your network via an Ethernet connection.

Apple appears to have quickly recognized the problem and has released a follow-up update which fixes this issue.

If you have the Incompatible Kernel Extension Configuration Data 3.28.1 update installed, but do not yet have the Incompatible Kernel Extension Configuration Data 3.28.2 update installed, the Ethernet drivers for your Mac will be blocked from running the next time the Mac is restarted. That will result in your Mac not being able to connect to your network via an Ethernet connection.

To fix this, the Incompatible Kernel Extension Configuration Data 3.28.2 update needs to be installed and the Mac rebooted again. After this reboot, the Ethernet drivers should be enabled again and your Mac’s Ethernet connection should work normally again.

When the Incompatible Kernel Extension Configuration Data 3.28.1 update is installed, the /System/Library/Extensions/AppleKextExcludeList.kext/Contents/Info.plist file is updated with the following entries, which add Apple’s Ethernet drivers to the kernel extension blacklist:

This just made my day! Had internet issues on Friday but when I got the internet back online display ethernet wasn’t working. Talk about timing I tried everything and then I see this article today!! Thanks.

Does anyone know if hand installing Incompatible Kernel Extension Configuration Data 3.28.2 (not Incompatible Kernel Extension Configuration Data 3.28.1) on an afflicted Mac and rebooting fixes this? I was able to get this update from a working Software Update server.